Simplify the following expression: ${6+3(3a+1)}$
Solution: Distribute the ${3}$ into the parentheses: $ 6 + {3(}\gray{3a+1}{)} $ $ 6 + {9a+3} $ Rewrite the expression to group the numeric terms: $ 9a + {6 + 3}$ Combine the numeric terms: $ 9a + {9}$ The simplified expression is $9a+9$